Apparatus and method for separating volumes of a composite liquid with a balancing assembly

ABSTRACT

Apparatus and method for balancing a centrifuge having interconnected hydraulic chambers in containers on a rotor, each container being adapted to receive a composite fluid, comprising transferring, by the rotation of the rotor, hydraulic liquid from a source to the interconnected hydraulic chambers to balance the centrifuge.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/US2006/021827 filed Jun. 5, 2006 which claims the benefit of U.S.provisional Application No. 60/693,320 filed Jun. 22, 2005.

FIELD OF THE INVENTION

The present invention relates to apparatus and a method for balancing acentrifuge.

BACKGROUND

The apparatus and method of the invention are particularly appropriatefor the separation of biological fluids comprising an aqueous componentand one or more cellular components. For example, potential uses of theinvention include: extracting a plasma component and a cellularcomponent (including platelets, white blood cells, and red blood cells)from a volume of whole blood, the cellular component being subsequentlyfiltered so as to remove platelets and white blood cells from the redblood cells; extracting a plasma component, in which a substantialamount of platelets is suspended, and a red blood cell component from avolume of whole blood, the white blood cells being subsequently removedby filtration from the platelet component and the red blood cellcomponent; extracting a plasma component, a platelet component, and ared blood cell component from a volume of whole blood, the white bloodcells being subsequently removed by filtration from the plateletcomponent and the red blood cell component.

An apparatus for processing blood components is known from document WO03/089027. This apparatus comprises a centrifuge adapted to cooperatewith an annular separation bag connected to at least one product bag,e.g. a platelet component bag.

The centrifuge includes a rotor having a turntable for supporting theseparation bag, and a central compartment for containing the product bagconnected to the separation bag; and a squeezing system for squeezingthe separation bag and causing the transfer of a separated component(e.g. platelets suspended in plasma) from the separation bag into theproduct bag.

With this apparatus, a single discrete volume of blood is processed atonce.

An object of the present invention is to design a separation apparatusthat can process at once at least two discrete volumes of a compositeliquid, in particular discrete volumes that may or may not be the same,and with the proportions of the various components of the compositeliquid that may vary from one discrete volume to another one. The objectof the invention is further to maintain the centrifuge that is part ofthe separation apparatus in balance even when the discrete volumesand/or the components are not the same.

One aspect of the invention relates to a balancing assembly for acentrifuge having a rotor and more than one container on the rotorwherein each container is adapted to receive a composite fluid. Thebalancing assembly comprises a source of hydraulic liquid; a rotor ductin the rotor directly connected to the source of hydraulic liquid; anhydraulic chamber in each container on the rotor wherein the hydraulicchambers are interconnected and are connected to the rotor duct; a motorfor rotating the rotor wherein rotation of the rotor causes hydraulicliquid to be transferred from the source to the interconnected hydraulicchambers to balance any unbalance in the rotor due to differences.

Another aspect of the invention relates to a method of balancing acentrifuge having a rotor and more than one containers on the rotorwherein each container contains a hydraulic chamber adapted to receive acomposite fluid. The method comprises interconnecting the hydraulicchambers; rotating the rotor and the containers on the rotor;transferring a volume of hydraulic liquid into the interconnectedhydraulic chambers comprising connecting a source of hydraulic liquid tothe interconnected hydraulic chambers, and distributing by the rotationof the rotor the hydraulic liquid from the source to the interconnectedhydraulic chambers.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a schematic view of a first set of bags designed forcooperating with a separation apparatus;

FIG. 2 is a schematic view of a second set of bags designed forcooperating with a separation apparatus;

FIGS. 3 a, 3 b are schematic views of two variants of a detail of theset of bags of FIG. 2;

FIG. 4 is a schematic view, partly in cross-section along a diametralplane, of a first embodiment of a separation apparatus;

FIG. 5 is a top view of the rotor of the separation apparatus of FIG. 4;

FIG. 6 is a perspective view of a first embodiment of a passivebalancing unit for a separation apparatus;

FIG. 7 is a perspective view of a second embodiment of a passivebalancing unit for a separation apparatus;

FIG. 8 is schematic view, in cross-section along a radial plane, of aseparation cell of the separation apparatus of FIGS. 4 and 5;

FIG. 9 is schematic view, in cross-section along a radial plane, of anembodiment of a separation cell adjacent to a storage container;

FIG. 10 is a perspective view of a rotor of a second embodiment of aseparation apparatus;

FIG. 11 is a cross-section view of the rotor of FIG. 10, along adiametral plane;

FIG. 12 is a top view of the rotor of FIG. 10;

FIG. 13 is a schematic view, in cross-section along a diametral plane,of a third embodiment of a separation apparatus;

FIG. 14 is schematic view, in cross-section along a radial plane, of aseparation cell of the separation apparatus of FIG. 13;

FIG. 15 is a perspective view of the flexible diaphragm of theseparation cell of FIG. 14;

FIGS. 16 to 18 are schematic views, in cross-section along a radialplane, of the separation cell FIG. 14 containing a separation bag atdifferent stages of a separation process; and

FIG. 19 is a schematic view, in cross-section along a diametral plane,of a fourth embodiment of a separation apparatus.

DESCRIPTION OF THE EMBODIMENTS

For the sake of clarity, the invention will be described with respect toa specific use, namely the separation of whole blood into at least twocomponents, in particular into a plasma component and a red blood cellcomponent, or into a plasma component, a platelet component and a redblood cell component. The discrete volume mentioned hereunder willtypically be the volume of a blood donation. The volume of a blooddonation may vary from one donor to another one (450 ml plus or minus10%). It is also recalled that the proportion of the components of bloodusually varies from one donor to another one, in particular thehematocrit, which is the ratio of the volume of the red blood cells tothe volume of the sample of whole blood considered. In other words thedensity of blood may slightly vary for one donor to another one. Itshould be understood however that this specific use is exemplary only.

FIG. 1 shows an example of a set of bags adapted to the separation of acomposite liquid (e.g. whole blood) into a first component (e.g. aplasma component containing or not a substantial amount of suspendedplatelets) and a second component (e.g. a blood cell component). Thisbag set comprises a flexible separation bag 1 and two flexible satellitebags 2, 3 connected thereto.

When the composite liquid is whole blood, the separation bag 1 has twopurposes, and is successively used as a collection bag and as aseparation bag. It is intended for initially receiving a discrete volumeof whole blood from a donor (usually about 450 ml) and to be used lateras a separation chamber in a separation apparatus. The separation bag 1is flat and generally rectangular. It is made of two rectangular sheetsof plastic material that are welded together so as to definetherebetween an interior space having a main rectangular portionconnected to a triangular top downstream portion. A first tube 4 isconnected to the tip of the triangular portion, and second and thirdtubes 5, 6 are connected to either lateral edges of the triangularportion, respectively. The proximal ends of the three tubes 4, 5, 6 areembedded between the two sheets of plastic material so as to beparallel. The separation bag 1 further comprises a hole 8 in each of itscorners that are adjacent to the three tubes 4, 5, 6. The holes 8 areused to secure the separation bag to a separation cell, as will bedescribed later.

The separation bag initially contains a volume of anti-coagulantsolution (typically about 63 ml of a solution of citrate phosphatedextrose for a blood donation of about 450 ml), and the first and thirdtubes 4, 6 are fitted at their proximal end with a breakable stopper 9,10 respectively, blocking a liquid flow therethrough.

The second tube 5 is a collection tube having a needle 12 connected toits distal end. At the beginning of a blood donation, the needle 12 isinserted in the vein of a donor and blood flows into the collection(separation) bag 1. After a desired volume of blood has been collectedin the collection (separation) bag 1, the collection tube 5 is sealedand cut.

The first satellite bag 2 is intended for receiving a plasma component.It is flat and substantially rectangular. It is connected to the distalend of the first tube 4.

The second satellite bag 3 is intended for receiving a red blood cellcomponent. It is flat and substantially rectangular. It is connected tothe distal end of the third tube 6. The third tube 6 comprises twosegments respectively connected to the inlet and the outlet of aleuko-reduction filter 13. The second satellite bag 3 contains a volumeof storage solution for red blood cells, and the third tube 6 is fittedat its distal end with a breakable stopper 14 blocking a liquid flowtherethrough.

FIG. 2 shows an example of a set of bags adapted to the separation of acomposite liquid (e.g. whole blood) into a first component (e.g. aplasma component), an intermediate component (e.g. a plateletcomponent), and a second component (e.g. a red blood cell component).This bag set comprises a flexible separation bag 1 and three flexiblesatellite bags 2, 3, 15 connected thereto.

This second set of bags differs from the set of bags of FIG. 1 in thatit comprises a third satellite bag 15, which is intended to receive aplatelet component, and a T-shaped three-way connector 16 having its legconnected by the first tube 4 to the separation bag 1, a first armconnected by a fourth tube 17 to the first satellite bag 2 (plasmacomponent bag), and a second arm connected by a fifth tube 18 to thethird satellite bag 15 (platelet component bag). Like the first andsecond satellite bags 2, 3, the third satellite bag 15 is flat andsubstantially rectangular.

FIGS. 3 a, 3 b show two variants of the T-shaped three-way connector 16of the bag set of FIG. 2.

The three-way connector 16 a shown in FIG. 3 a has the shape of aregular three-point star having a first outlet channel 21 and a secondoutlet channel 22 that are connected to an inlet channel 20 at an angleof about 120 degrees.

The three-way connector 16 b shown in FIG. 3 b, defines a first outletchannel 21 and a second outlet channel 22 that are perpendicularlyconnected to an inlet channel 20 and are offset along the inlet channel20 so that the first outlet channel 21 is further than the second outletchannel 22 from the end of the inlet channel 20 that is connected to thefirst tube 4.

The three-way connectors 16, 16 a, 16 b are arranged such that when theseparation bag of FIG. 2 (or any of its variants represented in FIG. 3a, 3 b) is mounted in a separation apparatus (to be described in detailbelow), in which a separation cell for a separation bag 1, a storagecontainer for the satellite bags 2, 3, 15, and a first and second pinchvalve members 70, 71 for allowing or stopping a flow of liquid in thefourth and fifth tubes 17, 18 are arranged in this order along a radialdirection from a rotation axis of the separation apparatus, with thepinch valve members being the closest to the rotation axis. In thisparticular configuration, when the fourth and fifth tubes 17, 18 areengaged in the first and second pinch valve members as shown in FIGS. 2,3 a, 3 b, then the three-way connector 16, 16 b, or a bend in the fourthand fifth tubes 17, 18 in the case of the connector 16 a of FIG. 3 a,are the closest portion(s) of the whole bag set to the rotation axis.The results of this disposition are that, when the separation apparatusrotates, any air in the bag set will gather in the connector in an areathat is the closest to the rotation axis (junction point of the threechannels 20, 21, 22 in the connectors shown in FIGS. 2, 3 b) or in thebends in the fourth and fifth tube 17, 18 between the connector and thepinch valve members 70, 71 when the connector used is the connector ofFIG. 3 a. This air buffer between the separation bag and the satellitebag will prevent any undesirable siphoning of contents of a satellitebag into the separation bag under centrifugation forces.

The three-way connector 16 b presents a particular interest when the bagset of FIG. 2 is used to separate a plasma component and a plateletcomponent. When the plasma component has been transferred into the firstsatellite bag 2 and the platelet component has been transferred into thethird satellite bag 15, the connector 16 b shown in FIG. 3 b allow forflushing the second channel 22, which may contain remaining platelets,with a small volume of plasma trapped in the fourth tube 17 between theconnector 16 b and the first pinch valve member.

FIGS. 4, 5, 6, 8 show a first embodiment of an apparatus forsimultaneously separating by centrifugation four discrete volumes of acomposite liquid. The apparatus comprises a centrifuge adapted toreceive four of either set of bags shown in FIGS. 1 and 2, with the fourdiscrete volumes of a composite liquid contained in the four separationbags; a component transferring means for transferring at least oneseparated component from each separation bag into a satellite bagconnected thereto; a first balancing means for initially balancing therotor when the weights of the four separation bags are different; and asecond balancing means for balancing the rotor when the weights of theseparated components transferred into the satellite bags cause anunbalance of the rotor.

The centrifuge comprises a rotor that is supported by a bearing assembly30 allowing the rotor to rotate around a rotation axis 31. The rotorcomprises a cylindrical rotor shaft 32 to which a pulley 33 isconnected; a storage means comprising a central cylindrical container 34for containing satellite bags, which is connected to the rotor shaft 32at the upper end thereof so that the longitudinal axis of the rotorshaft 32 and the longitudinal axis of the container 34 coincide with therotation axis 31, and a frusto-conical turntable 35 connected to theupper part of the central container 34 so that its central axiscoincides with the rotation axis 31. The frusto-conical turntable 35flares underneath the opening of the container 34. Four identicalseparation cells 40 are mounted on the turntable 35 so as to form asymmetrical arrangement with respect to the rotation axis 31.

The centrifuge further comprises a motor 36 coupled to the rotor by abelt 37 engaged in a groove of the pulley 33 so as to rotate the rotorabout the rotation axis 31.

Each separation cell 40 comprises a container 41 having the generalshape of a rectangular parallelepiped. The separation cells 40 aremounted on the turntable 35 so that their respective median longitudinalaxes 42 intersect the rotation axis 31, so that they are locatedsubstantially at the same distance from the rotation axis 31, and sothat the angles between their median longitudinal axes 42 aresubstantially the same (i.e. 90 degrees). The exact position of theseparation cells 40 on the turntable 35 is adjusted so that the weighton the turntable is equally distributed when the separation cells 40 areempty, i.e. so that the rotor is balanced. It results from thearrangement of the separating cells 40 on the turntable 35 that theseparating cells 40 are inclined with respect to the rotation axis 31 ofan acute angle equal to the angle of the frustum of a cone thatgeometrically defines the turntable 35.

Each container 41 comprises a cavity 43 that is so shaped anddimensioned as to loosely accommodate a separation bag 1 full of liquid,of the type shown in FIGS. 1 and 2. The cavity 43 (which will bereferred to later also as the “separation compartment”) is defined by abottom wall, that is the farthest to the rotation axis 31, a lower wallthat is the closest to the turntable 35, an upper wall opposite to thelower wall, and two lateral walls. The cavity 43 comprises a main part,extending from the bottom wall, which has substantially the shape of arectangular parallelepiped with rounded angles, and an upper part, whichhas substantially the shape of a prism having convergent triangularbases. In other words, the upper part of the cavity 43 is defined by twopairs of opposite walls converging towards the central median axis 42 ofthe cavity 43. One interest of this design is to cause a radialdilatation of the thin layer of a minor component of a composite fluid(e.g. the platelets in whole blood) after separation by centrifugation,and makes it more easily detectable in the upper part of a separationbag. The two pairs of opposite walls of the upper part of the separationcell 40 converge towards three cylindrical parallel channels 44, 45, 46,opening at the top of the container 41, and in which, when a separationbag 1 is set in the container 41, the three tubes 4, 5, 6 extend.

The container 41 also comprises a hinged lateral lid 47 (see FIGS. 8 and9), which is comprised of an upper portion of the external wall of thecontainer 41, i.e. the wall that is opposite to the turntable 35. Thelid 47 is so dimensioned as to allow, when open, an easy loading of aseparation bag 1 full of liquid into the separation cell 40. Thecontainer 41 comprises a fast locking means (not shown) by which the lid47 can be locked to the remaining part of the container 41.

The container 41 also comprises a securing means for securing aseparation bag 1 within the separation cell 40. The bag securing meanscomprises two pins 48 protruding on the internal surface of the lid 47,close to the top of separation cell 40, and two corresponding recesses49 in the upper part of the container 41. The two pins 48 are so spacedapart and dimensioned as to fit into the two holes 8 in the upper cornerof a separation bag 1.

The separation apparatus further comprises a component transferringmeans for transferring at least one separated component from eachseparation bag into a satellite bag connected thereto. The componenttransferring means comprises a squeezing system for squeezing theseparation bags 1 within the separation compartments 43 and causing thetransfer of separated components into satellite bags 2, 3, 15.

The squeezing system comprises a flexible diaphragm 50 that is securedto each container 41 so as to define an expandable chamber 51 in thecavity thereof. More specifically, the diaphragm 50 is dimensioned so asto line the bottom wall of the cavity 43 and a large portion of thelower wall of the cavity 43, which is the closest to the turntable 35.

The squeezing system further comprises a peripheral circular manifold 52that forms a ring within the turntable 35 extending close to theperiphery of the turntable 35. Each expansion chamber 51 is connected tothe manifold 52 by a supply channel 53 that extends through the wall ofthe respective container 41, close to the bottom thereof.

The squeezing system further comprises a hydraulic pumping station 60for pumping a hydraulic liquid in and out of the expandable chambers 51within the separation cells 40. The hydraulic liquid is selected so asto have a density slightly higher than the density of the more dense ofthe components in the composite liquid to be separated (e.g. the redblood cells, when the composite liquid is blood). As a result, duringcentrifugation, the hydraulic liquid within the expandable chambers 51,whatever the volume thereof, will generally remain in the most externalpart of the separation cells 40. The pumping station 60 is connected tothe expandable chambers 51, through a rotary seal 69, by a duct 56 thatextends through the rotor shaft 32, the bottom and lateral wall of thecentral container 34, and, from the rim of the central container 34,radially through the turntable 35 where it connects to the manifold 52.

The pumping station 60 comprises a piston pump having a piston 61movable in a hydraulic cylinder 62 fluidly connected via a rotary fluidcoupling 63 to the rotor duct 54. The piston 61 is actuated by a steppermotor 64 that moves a lead screw 65 linked to the piston rod. Thehydraulic cylinder 62 is also connected to a hydraulic liquid reservoir66 having an access controlled by a valve 67 for selectively allowingthe introduction or the withdrawal of hydraulic liquid into and from ahydraulic circuit including the hydraulic cylinder 62, the rotor duct 56and the expandable hydraulic chambers 51. A pressure gauge 68 isconnected to the hydraulic circuit for measuring the hydraulic pressuretherein.

The separation apparatus further comprises four pairs of a first andsecond pinch valve members 70, 71 that are mounted on the rotor aroundthe opening of the central container 34. Each pair of pinch valvemembers 70, 71 faces one separation cell 40, with which it isassociated. The pinch valve members 70, 71 are designed for selectivelyblocking or allowing a flow of liquid through a flexible plastic tube,and selectively sealing and cutting a plastic tube. Each pinch valvemember 70, 71 comprises an elongated cylindrical body and a head havinga groove 72 that is defined by a stationary upper jaw and a lower jawmovable between an open and a closed position. The groove 72 is sodimensioned that one of the tubes 4, 17, 18 of the bag sets shown inFIGS. 1 and 2 can be snuggly engaged therein when the lower jaw is inthe open position. The elongated body contains a mechanism for movingthe lower jaw and it is connected to a radio frequency generator thatsupplies the energy necessary for sealing and cutting a plastic tube.The pinch valve members 70, 71 are mounted inside the central container34, adjacent the interior surface thereof, so that their longitudinalaxes are parallel to the rotation axis 31 and their heads protrude abovethe rim of the container 34. The position of a pair of pinch valvemembers 70, 71 with respect to a separation bag 1 and the tubes 4, 17,18 connected thereto when the separation bag 1 rests in the separationcell 40 associated with this pair of pinch valve members 70, 71 is shownin doted lines in FIGS. 1 and 2. Electric power is supplied to the pinchvalve members 70, 71 through a slip ring array 38 that is mounted arounda lower portion of the rotor shaft 32.

The separation apparatus further comprises four pairs of sensors 73, 74for monitoring the separation of the various components occurring withineach separation bag when the apparatus operates. Each pair of sensors73, 74 is embedded in the lid 47 of the container 41 of each separationcell 40 along the median longitudinal axis 42 of the container 41, afirst sensor 73 being located the farthest and a second sensor 74 beinglocated the closest to the rotation axis 31. When a separation bag 1rests in the container 41 and the lid 47 is closed, the first sensor 73(later the bag sensor) faces the upper triangular part of the separationbag 1 and the second sensor 74 (later the tube sensor) faces theproximal end of the first tube 4. The bag sensor 73 is able to detectblood cells in a liquid. The tube sensor 74 is able to detect thepresence or absence of liquid in the tube 4 as well as to detect bloodcells in a liquid. Each sensor 73, 74 may comprise a photocell includingan infrared LED and a photo-detector. Electric power is supplied to thesensors 73, 74 through the slip ring array 38 that is mounted around thelower portion of the rotor shaft 32.

The separation apparatus further comprises a first balancing means forinitially balancing the rotor when the weights of the four separationbags 1 contained in the separation cells 40 are different. The firstbalancing means substantially comprises the same structural elements asthe elements of the component transferring means described above,namely: four expandable hydraulic chambers 51 interconnected by aperipheral circular manifold 52, and a hydraulic liquid pumping station60 for pumping hydraulic liquid into the hydraulic chambers 51 through arotor duct 56, which is connected to the circular manifold 52. In orderto initially balance the rotor, whose four separation cells 40 containfour discrete volumes of a composite liquid that may not have the sameweight (because the four volumes may be not equal, and/or the density ofthe liquid may slightly differ from one volume to the other one), thepumping station 60 is controlled so as to pump into the interconnectedhydraulic chambers 51, at the onset of a separation process, apredetermined volume of hydraulic liquid that is so selected as tobalance the rotor in the most unbalanced situation. For whole blood, thedetermination of this balancing volume takes into account the maximumdifference in volume between two blood donations, and the maximumdifference in hematocrit (i.e. in density) between two blood donations.Under centrifugation forces, the hydraulic liquid will distributeunevenly in the four separation cells 40 depending on the difference inweight of the separation bags 1, and balance the rotor. In order to getan optimal initial balancing, the volume of the cavity 43 of theseparation cells 40 should be selected so that the cavities 43, whateverthe volume of the separation bags 1 contained therein, are not fullafter the determined amount of hydraulic liquid has been pumped into theinterconnected expansion chambers 51.

The separation apparatus further comprises a second balancing means, forbalancing the rotor when the weights of the components transferred intothe satellite bags 2, 3, 15 in the central container 34 are different.For example, when two blood donations have the same hematocrit anddifferent volumes, the volumes of plasma extracted from each donationare different, and the same is true when two blood donations have thesame volume and different hematocrit. As shown in FIGS. 4, 5, 6 thesecond balancing means comprises four flexible rectangular pouches 81,82, 83, 84 that are interconnected by four tube sections 85, 86, 87, 88,each tube section connecting two adjacent pouches by the bottom thereof.The pouches 81, 82, 83, 84 contain a volume of balancing liquid having adensity close to the density of the composite liquid. The volume ofbalancing liquid is so selected as to balance the rotor in the mostunbalanced situation. The four pouches 81, 82, 83, 84 are so dimensionedas to line the inner surface of the central container 34 and to have aninternal volume that is larger than the volume of balancing liquid sothat the balancing liquid can freely expand in any of the pouches 81,82, 83, 84. In operation, if, for example, four satellite bags 2respectively adjacent to the four pouches 81, 82, 83, 84 receivedifferent volumes of a plasma component, the four satellite bags 2 willpress unevenly, under centrifugation forces, against the four pouches81, 82, 83, 84, which will result in the balancing liquid becomingunevenly distributed in the four pouches 81, 82, 83, 84 and compensatingfor the difference in weight in the satellite bags 2.

The separation apparatus further comprises a controller 90 including acontrol unit (e.g. a microprocessor) and a memory unit for providing themicroprocessor with information and programmed instructions relative tovarious separation protocols (e.g. a protocol for the separation of aplasma component and a blood cell component, or a protocol for theseparation of a plasma component, a platelet component, and a red bloodcell component) and to the operation of the apparatus in accordance withsuch separation protocols. In particular, the microprocessor isprogrammed for receiving information relative to the centrifugationspeed(s) at which the rotor is to be rotated during the various stagesof a separation process (e.g. stage of component separation, stage of aplasma component expression, stage of suspension of platelets in aplasma fraction, stage of a platelet component expression, etc), andinformation relative to the various transfer flow rates at whichseparated components are to be transferred from the separation bag 1into the satellite bags 2, 3, 15. The information relative to thevarious transfer flow rates can be expressed, for example, as hydraulicliquid flow rates in the hydraulic circuit, or as rotation speeds of thestepper motor 64 of the hydraulic pumping station 60. The microprocessoris further programmed for receiving, directly or through the memory,information from the pressure gauge 68 and from the four pairs ofphotocells 73, 74 and for controlling the centrifuge motor 36, thestepper motor 64 of the pumping station 60, and the four pairs of pinchvalve members 70, 71 so as to cause the separation apparatus to operatealong a selected separation protocol.

Variants of the first embodiment of the separation apparatus describedabove are as follows:

Instead of the centralized hydraulic squeezing system described above, aseparation apparatus can be fitted with as many independent squeezingmeans as separation cells 40. An independent squeezing means may becomprised, for example, of a plate that can be moved by anyelectro-magnetic, electro-mechanical or hydraulic mechanism so as tosqueeze a separation bag against a wall of the cavity 43 of thecontainer 41 of a separation cell 40.

Instead of a system of interconnected hydraulic chambers or pouches, thefirst and/or second balancing means can comprise a ball balancerincluding a circular cage in which heavy balls can move freely. Thecircular cage is mounted on the rotor so as to be centered on therotation axis 31.

Instead of a central container 34 for containing all the satellite bags2, 3, 15 connected to the separation bags 1, a separation apparatus cancomprise as many satellite bag containers as separation cells. FIG. 9shows a container arrangement that can be used in such a separationapparatus. The container arrangement of FIG. 9 comprises a separationbag container 41 that is connected to or is made integral with asatellite bag container 54. The satellite bag container 54 comprises acavity 55 having the shape of a rectangular parallelepiped, whichcontains a pouch 81 of a balancing assembly as shown in FIG. 6. Theseparation bag container 41 is superimposed on the satellite bagcontainer 54 so that the openings of both containers are in the sameplane, facing the rotation axis 31 when the container arrangement ismounted on a rotor turntable 35.

The second sensors 74 can be embedded in the lids 47 of the containers41 so as to face an upper part of a separation bag 1 close to theconnection thereof to the first tube 4.

The diaphragm 50, instead of being secured to the container 41 so as toline a portion of the lower wall of the cavity 43, can be secured to thecontainer 41 so as to line a portion of the upper wall of the cavity 43.

In each separation cell 40, the hydraulic chamber 51, instead of beingdefined by a flexible diaphragm 50 lining the bottom wall of the cavity43 and a large portion of the lower wall of the cavity 43, can comprisea flexible pouch similar to a pouch of the second balancing means.

The second balancing means, instead of comprising four interconnectedpouches 81, 82, 83, 84 as shown in FIG. 6, can comprise a flexibletubular pouch 80 having two concentric walls as shown in FIG. 7. Thepouch 80 is so dimensioned as to line the inner surface of the centralcontainer 34 and to have an internal volume that is larger than thevolume of balancing liquid so that the balancing liquid can freelyexpand in one area of pouch or in another.

The pumping station 60, instead of a piston pump 61, 62, can compriseany pump (e.g. a positive displacement pump) whose output can becontrolled with sufficient accuracy.

FIGS. 10, 11, 12 show the rotor of a second embodiment of a separationapparatus for four discrete volumes of a composite liquid.

The rotor of this second embodiment essentially differs from the rotorof the embodiment of FIGS. 4 and 5 in the spatial arrangement of thepinch valve members 70, 71 and of the storage means for the satellitebags with respect to the separation cells 40. In this embodiment, thestorage means, instead of comprising a central container, comprises foursatellite containers 341, 342, 343, 344 that are arranged around acentral cylindrical cavity 340, in which the four pairs of pinch valvemember 70, 71 are mounted with their longitudinal axes parallel to therotation axis 31. The cavity 43 of a satellite container 341, 342, 343,344 has a regular bean-like cross-section, and a central longitudinalaxis that is parallel to the rotation axis 31 and intersects thelongitudinal axis 42 of the associated separation cell 40.

When a set of bag as shown in FIGS. 2, 3 a, 3 b is mounted on the rotorof FIGS. 11 to 12, the separation bag 1 and the satellite bags 2, 3, 15are located beyond the associated pinch valves members 70, 71 withrespect to the rotation axis 31. The tubes 4, 17, 18 and the three-wayconnector 16, 16 a, 16 b connecting the bags are then in the positionshown in FIGS. 2, 3 a, 3 b.

The operation of the separation apparatus of FIGS. 3 and 4, inaccordance to a first and second an illustrative separation protocols,will be described now.

According to a first separation protocol, four discrete volumes of bloodare separated into a plasma component, a first cell component comprisingplatelets, white blood cells, some red blood cells and a small volume ofplasma (later the “buffy coat” component) and a second cell componentmainly comprising red blood cells. Each volume of blood is contained ina separation bag 1 of a bag set represented in FIG. 2, in which it haspreviously been collected from a donor using the collection tube 5.After the blood collection, the collection tube 5 has been sealed andcut close to the separation bag. Typically, the volumes of blood are notthe same in the four separation bags 1, and the hematocrit varies fromone separation bag 1 to another one. Consequently, the separation bags 1have slightly different weights.

First stage (first protocol): setting the four bag sets in theseparation apparatus

Four separation bags 1 are loaded into the four separation cells 40. Thelids 47 are closed and locked, whereby the separation bags 1 are securedby their upper edge to the containers 41 (the pins 48 of the securingmeans pass then through the holes 8 in the upper corner of theseparation bags 1 and engage the recesses 49 or the securing means).

The tubes 17 connecting the separations bags 1 to the plasma componentbags 2, through the T connectors 16, are inserted in the groove 72 ofthe first pinch valve members 70. The tubes 18 connecting theseparations bags 1 to the buffy coat component bags 15, through the Tconnector 16, are inserted in the groove 72 of the second pinch valvemembers 71. The four plasma component bags 2, the four buffy coatcomponent bags 15, the four red blood cell component bags 3 and the fourleuko-reduction filters 13 are inserted in the central compartment 34 ofthe rotor. The four plasma component bags 2 are respectively placed indirect contact with the pouches 81 to 84 of the second balancing means.The pinch valve members 70, 71 are closed and the breakable stoppers 9in the tubes 4 connecting the separation bags 1 to the T connectors 16are manually broken.

Second Stage (First Protocol): Balancing the Rotor in Order toCompensate for the Difference in Weights of the Separation Bags

At the onset of the second stage, all the pinch valve members 70, 71 areclosed. The rotor is set in motion by the centrifuge motor 36 and itsrotation speed increases steadily until it rotates at a firstcentrifugation speed. The pumping station 60 is actuated so as to pump apredetermined overall volume of hydraulic liquid into the four hydraulicchambers 51, at a constant flow rate. This overall volume of liquid ispredetermined taking into account the maximum variation of weightbetween blood donations, so that, at the end of the second stage, theweights in the various separation cells 40 are substantially equal andthe rotor is substantially balanced, whatever the specific weights ofthe separation bags 1 that are loaded in the separation cells 40. Notethat this does not imply that the internal cavity 43 of the separationcells 40 should be filled up at the end of the balancing stage. For thepurpose of balancing the rotor, it suffices that there is enoughhydraulic liquid in the separation cells 40 for equalizing the weightstherein, and it does not matter if an empty space remains in eachseparation cell 40 (the size of this empty space essentially depends onthe volume of the internal cavity 43 of a separation cell 40 and theaverage volume of a blood donation). Because the hydraulic chambers 51are interconnected, the distribution of the overall volume of hydraulicliquid between the separations chambers 40 simply results from therotation of the rotor. When the weights of the separation bags 1 are thesame, the distribution of the hydraulic liquid is even. When they arenot, the distribution of the hydraulic liquid is uneven, and the smallerthe weight of a specific separation bag 1, the larger the volume of thehydraulic fluid in the associated hydraulic chamber 51.

Third Stage (First Protocol): the Blood Within the Separation Bags 1 isSedimented to a Desired Level.

At the onset of this stage, all pinch valve members 70, 71 are closed.The rotor is rotated at a second centrifugation speed (highsedimentation speed or “hard spin”) for a predetermined period of timethat is so selected that, whatever the hematocrit of the blood in theseparation bags 1, the blood sediments in each of the separation bag 1at the end of the selected period to a point where the hematocrit of theouter red blood cell layer is about 90 and the inner plasma layer doesnot substantially contain anymore cells, the platelets and the whiteblood cells forming then an intermediary layer between the red bloodcell layer and the plasma layer.

Fourth Stage (First Protocol): a Plasma Component is Transferred intothe Plasma Component Bags 2.

At the onset of this stage, the rotation speed is decreased to a thirdcentrifugation speed, the four first pinch valve members 70 controllingaccess to the plasma component bags 2 are opened, and the pumpingstation 60 is actuated so as to pump hydraulic liquid at a firstconstant flow rate into the hydraulic chambers 51 and consequentlysqueeze the separation bags 1 and cause the transfer of plasma into theplasma component bags 2.

When blood cells are detected by the bag sensor 73 in the separationcell 40 in which this detection occurs first, the pumping station 60 isstopped and the corresponding first pinch valve member 70 is closed,either immediately or after a predetermined amount of time selected inview of the volume of plasma that it is desirable in the buffy coatcomponent to be expressed in a next stage.

Following the closure of the first (first) pinch valve member 70 (i.e.the first pinch valve of the group of first pinch valve members 70) toclose, the pumping station 60 is actuated anew so as to pump hydraulicliquid at a second, lower, flow rate into the hydraulic chambers 51 andconsequently squeeze the three separation bags 1 whose outlet is notclosed by the corresponding first pinch valve members 70.

When blood cells are detected by the bag sensor 73 in the separationcell 40 in which this detection occurs second, the pumping station 60 isstopped and the corresponding first pinch valve member 70 is closed(same timing as for the closing of the first (first) pinch valve memberto close).

Following the closure of the second (first) pinch valve member 70 toclose, the pumping station 60 is actuated anew so as to pump hydraulicliquid at the second flow rate into the hydraulic chambers 51 andconsequently squeeze the two separation bags 1 whose outlet is notclosed by the corresponding first pinch valve members 70.

When blood cells are detected by the bag sensor 73 in the separationcell 40 in which this detection occurs third, the pumping station 60 isstopped and the corresponding first pinch valve member 70 is closed(same timing as for the closing of the first (first) pinch valve memberto close).

Following the closure of the third (first) pinch valve member 70 toclose, the pumping station 60 is actuated anew so as to pump hydraulicliquid at the second flow rate into the hydraulic chambers 51 andconsequently squeeze the separation bag 1 whose outlet is not yet closedby the corresponding first pinch valve member 70.

When blood cells are detected by the bag sensor 73 in the separationcell 40 in which this detection occurs last, the pumping station 60 isstopped and the corresponding first pinch valve member 70 is closed(same timing as for the closing of the first pinch valve member toclose).

In the plasma component transfer process described above, the transferof the four plasma components starts at the same time, run in partsimultaneously and stop independently of each other upon the occurrenceof a specific event in each separation bag (detection of blood cells bythe bag sensor).

As a variant, when the second flow rate is sufficiently low and theclosing of the first pinch valve member 70 occurs almost simultaneouslywith the detection of blood cells in the separation bags, then thepumping station can be continuously actuated during the fourth stage.

The fourth stage ends when the four first pinch valve members 70 areclosed.

Fifth Stage (First Protocol): a Buffy Coat Component is Transferred intothe Buffy Coat Component Bags 15.

The control unit 90 is programmed to start the fifth stage after thefour first pinch valve members 70 are closed, upon receiving informationfrom the last bag sensor 73 to detect blood cells.

At the onset of this stage, the rotation speed remains the same (thirdcentrifugation speed), a first of the four second pinch valve members 71controlling access to the buffy coat component bags 15 is opened, andthe pumping station 60 is actuated so as to pump hydraulic liquid at athird constant flow rate into the hydraulic chambers 51 and consequentlysqueeze the separation bag 1 in the separation cell 40 associated withthe opened second pinch valve members 71 and cause the transfer of thebuffy coat component into the buffy coat component bag 2 connected tothis separation bag 1.

After a predetermined period of time after blood cells are detected bythe tube sensor 74 in the separation cell 40 associated with the openedsecond pinch valve member 71, the pumping station 60 is stopped and thesecond pinch valve member 71 is closed.

After the first (second) pinch valve member 71 has closed (i.e. thefirst pinch valve of the group of second pinch valve members 71), asecond (second) pinch valve member 71 is opened, and a second buffy coatcomponent is transferred into a buffy coat component bag 2, in the sameway as above.

The same process is successively carried out to transfer the buffy coatcomponent from the two remaining separation bags 1 into the buffy coatcomponent bag 2 connected thereto.

In the buffy coat component transfer process described above, thetransfers of the four buffy coat components are successive, and theorder of succession is predetermined. However, each of the second, thirdand four transfers starts following the occurrence of a specific eventat the end of the previous transfer (detection of blood cells by thetube sensor 74 or closing of the second valve member 71).

As a variant, when the third flow rate is sufficiently low and theclosing of the second pinch valve members 71 occurs almostsimultaneously with the detection of blood cells in the tubes 4, thenthe pumping station can be actuated continuously during the fourthstage.

As a variant, the control unit 90 is programmed to start the fifth stageafter a predetermined period of time after receiving information fromthe first (or the second or the third) bag sensor 73 to detect bloodcells. The period of time is statistically or empirically determined sothat, whatever the event from which it starts running (detection of theblood cells by either one of the first, second, and third bag sensor 73to detect blood cells), the four first pinch valve members 70 are closedwhen it is over.

The fifth stage ends when the four second pinch valve members 71 areclosed.

Sixth Stage (First Protocol): the Centrifugation Process is Ended.

The control unit 90 is programmed to start the sixth stage after thefour (second) pinch valve members 71 are closed, upon receivinginformation from the last tube sensor 74 to detect blood cells.

The rotation speed of the rotor is decreased until the rotor stops, thepumping station 60 is actuated so as to pump the hydraulic liquid fromthe hydraulic chambers 51 at a high flow rate until the hydraulicchambers 51 are empty, and the first and second pinch valve members 70,71 are actuated so as to seal and cut the tubes 17, 18. The blood cellsremain in the separation bags 1.

When the fifth stage is completed, the four bag sets are removed fromthe separation apparatus and each bag set is separately handledmanually.

The breakable stopper 10 blocking the communication between theseparation bag 1 and the tube 6 connected thereto is broken, as well asthe breakable stopper 14 blocking the communication between the secondsatellite bag 3 and the tube 6. The storage solution contained in thesecond satellite bag 3 is allowed to flow by gravity through theleuko-reduction filter 13 and into the separation bag 1, where it ismixed with the red blood cells so as to lower the viscosity thereof. Thecontent of the separation bag 1 is then allowed to flow by gravitythrough the filter 13 and into the second satellite bag 3. The whiteblood cells are trapped by the filter 13, so that substantially only redblood cells are collected into the second satellite bag 3.

As a variant, the control unit 90 is programmed to start the sixth stageafter a predetermined period of time after receiving information fromthe first (or the second or the third) tube sensor 74 to detect bloodcells. The period of time is statistically or empirically determined sothat, whatever the event from which it starts running (detection of theblood cells by either one of the first, second, and third tube sensor 74to detect blood cells), the four second pinch valve members 71 areclosed when it is over.

According to a second separation protocol, four discrete volumes ofblood are separated into a plasma component, a platelet component and ared blood cell component. Each volume of blood is contained in aseparation bag 1 of a bag set represented in FIG. 2, in which it haspreviously been collected from a donor using the collection tube 5.After the blood collection, the collection tube 5 has been sealed andcut close to the separation bag 1. Typically, the volumes of blood arenot the same in the four separation bags 1, which, consequently, haveslightly different weights. Also, typically, the hematocrit varies fromone separation bag 1 to another one.

First stage (second protocol): setting the four bag sets in theseparation apparatus

This stage is identical to the first stage of the first protocol.

Second stage (second protocol): balancing the rotor in order tocompensate for the difference in weights of the separation bags

This stage is identical to the second stage of the first protocol.

Third stage (second protocol): the blood within the separation bags 1 issedimented to a desired level.

This stage is identical to the third stage of the first protocol.

Fourth stage (second protocol): a first, larger, portion of plasma istransferred into the plasma bags 2, while a second, smaller, portion ofplasma remains in the separation bags 1. This stage is substantially thesame as the fourth stage of the first protocol. However, the expressionof plasma from each separation bag 1 into the attached plasma componentbag 2 is stopped immediately after detection of blood cells by thecorresponding bag sensor 73, so that the volume of plasma remaining inthe separation bag 1 is large enough to allow the platelets to bere-suspended therein.Fifth stage (second protocol): a platelet component is prepared in theseparation bag 1.

At the onset of this fifth stage, the first and second valve members 70,71 are closed. The rotor is stopped and the pumping station 60 isactuated so as to pump a volume of hydraulic liquid from the hydraulicchambers 51 at a high flow rate. The rotor is then controlled so as tooscillate back and forth around the rotation axis 31 for a determinedperiod of time, at the end of which the cells in the separation bags 1are substantially suspended in plasma. The rotor is then set in motionagain by the centrifuge motor 36 so that its rotation speed increasessteadily until it reaches a fourth centrifugation speed (lowsedimentation speed or “soft spin”). The rotor is rotated at the fourthrotation speed for a predetermined period of time that is selected sothat the blood sediments in the separation bags 1 at the end of theselected period to a point where the separation bags 1 exhibit an outerlayer comprising packed red blood cells and an inner annular layersubstantially comprising platelets suspended in plasma.

Sixth stage (second protocol): a platelet component is transferred intothe platelet bags 15. This stage is substantially the same as the fifthstage of the first protocol (buffy coat expression).

Seventh stage (second protocol): the centrifugation process is ended.

This stage is substantially the same as the sixth stage of the firstprotocol.

FIGS. 13 to 18 show a third embodiment of a separation apparatus forfour discrete volumes of a composite liquid.

The separation apparatus of FIG. 13 to 18 is particularly adapted to theseparation of a composite fluid in two components, for example theseparation of whole blood into a cell component (red blood cells, whitecells and platelets) and a plasma component substantially devoid ofcells or the separation of whole blood into a cell component (red bloodcells, white cells and a small amount of platelets) and a plasmacomponent containing a large amount of platelets in suspension.

The main differences between the first separation apparatus shown inFIGS. 4 and 5 and the third separation apparatus shown in FIGS. 13 to 18are as follows. The shape of the separation cells 100 of the thirdseparation apparatus is different from the shape of the separation cells40 of the first separation apparatus. Each of the separation cells 100of the third separation apparatus is associated with one pinch valvemember 70 and one tube sensor 74. The third separation apparatus doesnot comprise a pumping station for pumping a hydraulic liquid in and outof the hydraulic chambers of the separation cells 100.

In more details, a separation cell 100 for the third separationapparatus comprises a container 101 having the general shape of arectangular parallelepiped. The cavity (also referred to as the“separation compartment”) of the container 101, which has also thegeneral shape of a rectangular parallelepiped, is so dimensioned as toloosely accommodate a separation bag 1 full of liquid, of the type shownin FIG. 2. The separation cell 100 further comprises an elasticdiaphragm 110, which defines within the cavity of the container 101 afirst chamber 102 for receiving a separation bag 1, and a secondhydraulic chamber 103 that is connected to the peripheral manifold 52,through an inlet aperture 104 close to the bottom of the container 101.The separation cell 100 further comprises a lid having two flaps 105,106 that are hinged to the longer parallel sides of the opening of thecontainer 101. The two flaps 105, 106 can be locked in a closed positionby a locking means (not shown). The separation cell 100 furthercomprises a securing means for securing a separation bag 1 within theseparation cell 100.

The bag securing means comprises two pins 107 and two correspondingrecesses 108 that respectively protrude or open on the edges of theflaps 105, 106 that face each other when the lid is closed. The two pins107 are so spaced apart and dimensioned as to fit into the two holes 8in the upper corner of a separation bag 1. The two flaps 105, 106 alsocomprise on their facing edges three semi-cylindrical holes 109 foraccommodating the proximal end of three tubes 4, 5, 6 embedded in theupper area of a separation bag 1. The outer flap 106 includes a cavityfacing the median semi-cylindrical hole 109, for containing the bagsensor 74.

As shown in FIGS. 15 to 18, the diaphragm 110 comprises a flatrectangular socket 111 almost as wide as a separation cell 100. Thediaphragm 110 further comprises a large, rectangular, connecting portion112 extending around the mouth of the socket 111, perpendicularly to thesocket 111 when the diaphragm 110 is not deformed by a separation bag 1and it is held in an upright position (FIG. 15). The socket 111 isconnected to the connecting portion 112 along the longitudinal medianaxis thereof. The connecting portion 112 has a surface slightly largerthan a transversal cross-section of the cavity of the container 101. Thediaphragm 110 is tightly attached to the top of the container 101 by aperipheral area of the connecting portion 112. The diaphragm 110 is madeof an elastic and deformable elastomeric material so selected that thediaphragm 110 conforms very closely the shape of a separation bag 1before and during centrifugation and as shown in FIGS. 16 to 18.

As mentioned above, the separation apparatus shown in FIG. 13 does notcomprise a pumping station for pumping a hydraulic fluid in and out ofthe hydraulic chambers 103. Instead, it comprises a reservoir 120 forhydraulic liquid, which is fixed with respect to the rotor, and which isdirectly connected to the rotor duct 56 by a conduit 121 and a rotaryseal 122. The conduit 121 is fitted with a valve 123. The reservoir 120is secured to a frame of the separation apparatus so as to be lower thanthe four separation cells 100. When the separation apparatus is used forseparating red blood cells from plasma (with or without suspendedplatelets), the density of the hydraulic liquid is selected, for reasonsexplained below, so as to be between the density of packed red bloodcells and the density of plasma.

The component transferring means of the third separation apparatusessentially comprises the reservoir 120 that is directly connected tothe rotor duct 56 by the rotary seal 122, the hydraulic chambers 103,and the motor 36 that drives the rotor in rotation. When the valve 123is opened and the rotation speed of the rotor reaches a determinedthreshold, which depends on the height between the reservoir 120 and theseparation cells 100 and the distance between the rotation axis 31 andthe separation cells 100, then the hydraulic liquid flows from thereservoir 120 into the hydraulic chambers 103 so as to fill up thehydraulic chamber 103 and squeeze the separation bags 1 therein,whatever the volume/weight of the separation bags 1. The speed thresholdis substantially below the rotation speed at which the rotor is rotatedfor separating blood components (“high spin” as well as “soft spin). Thetransfer of a separated component from a separation bag 1 into asatellite bag 2 is then controlled by the opening/closing of the pinchvalve member 70 in which the tube 4 connecting the two bags is inserted.

The first balancing means of the third separation apparatus essentiallycomprises the reservoir 120 that is directly connected to the rotor duct56 through the rotary seal 122, the hydraulic chambers 103, the motor 36that drives the rotor in rotation, and the valve 123. At the onset of aseparation process, the valve 123 is opened for a predetermined periodof time so as to allow the transfer, in the interconnected hydraulicchambers 103, of a predetermined volume of hydraulic liquid that is soselected as to balance the rotor in the most unbalanced situation. Forwhole blood, the determination of this balancing volume takes intoaccount the maximum difference in volume between two blood donations,and the maximum difference in hematocrit (i.e. in density) between twoblood donations.

A variant of the third embodiment of a separation apparatus does notcomprise a valve 123 on the conduit 121 connecting the reservoir 120 tothe rotor duct 56. As a result, when the threshold speed is reached, thehydraulic liquid is pumped from the reservoir 120 into the hydraulicchambers 103 until the pressure that is building up within theseparation cells 100 prevents further pumping. The filling up of thespace available in the separation cells 100 with hydraulic liquid mightnot however result in an optimal balance of the rotor depending, inparticular, on the difference in weight of the separation bags 1, oftheir volume, and of the density of the hydraulic liquid.

The operation of the third separation apparatus, in accordance to athird illustrative separation protocol, will be described now.

According to a third separation protocol, four discrete volumes of bloodare separated into a plasma component (including or not including asubstantial amount of platelets) and a blood cell component (includingplatelets, or residual platelets, white blood cells and red bloodcells). Each volume of blood is contained in a separation bag 1 of a bagset represented in FIG. 1, in which it has previously been collectedfrom a donor using the collection tube 5. After the blood collection,the collection tube 5 has been sealed and cut close to the separationbag 1. Typically, the volumes of blood are not the same in the fourseparation bags 1 and the hematocrit varies from one separation bag 1 toanother one. As a result, the separation bags have slightly differentweights.

First stage (third protocol): setting the four bag sets in theseparation apparatus

Four separation bags 1 are inserted into the socket 111 of a diaphragm110 within the four separation cells 100 as shown in FIG. 16. The twoflaps 105, 106 of the lids of the separation cells 100 are closed andconsequently secure the top of the separation bags 1 to the separationcells 100. The tube sensors 74 embedded in the outer flap 106 of thelids now face the proximal end of the tubes 4 connecting the separationbags 1 to the plasma component bags 2. The tubes 4 are inserted in thegroove 72 of the pinch valve members 70. The four plasma component bags2, the four red blood cell component bags 3 and the four leuko-reductionfilters 13 are inserted in the central compartment 34 of the rotor. Thepinch valve members 70 are closed and the breakable stoppers 9 in thetubes 4 connected to the plasma component bags 2 are manually broken.

Second Stage (Third Protocol): Balancing the Rotor in Order toCompensate for the Difference in Weights of the Separation Bags

At the onset of this second stage, the pinch valve members 70, in whichthe tubes 4 are engaged, are closed. The valve 123 on the conduitconnecting the reservoir 120 to the rotor duct 56 is opened. The rotoris set in motion by the centrifuge motor 36 and its rotation speedincreases steadily until it rotates at a predetermined sedimentationspeed. Before it rotates at the sedimentation speed, the rotor reaches athreshold speed at which its rotation causes the pumping of hydraulicliquid from the reservoir 120 into the interconnected hydraulic chambers103 of the separation cells 100. The valve is closed 123 after apredetermined amount of hydraulic fluid sufficient for balancing therotor has been transferred in the hydraulic chambers 103. Because thehydraulic chambers 103 are interconnected by the peripheral manifold 52,the hydraulic liquid gets automatically distributed in the separationcells 100 so as to balance the rotor. When the weights of the separationbags 1 are the same, the distribution of the hydraulic liquid is even.When they are not, the distribution of the hydraulic liquid is uneven,and the smaller the weight of blood in a specific separation bag 1, thelarger the volume of the hydraulic fluid in the associated hydraulicchamber 103.

Third Stage (Third Protocol): the Blood Within the Separation Bags 1 isSedimented to a Desired Level.

When it is desired to separate a plasma component containing a largeamount of suspended platelets (“platelet rich plasma”) and a cellcomponent mainly containing red blood cells and white blood cells, therotor is rotated at a first sedimentation speed (about 2000 RPM, usuallyreferred to as “soft spin”).

When it is desired to separate a plasma component substantially devoidof cells (“platelet poor plasma”) and a cell component containing redblood cells, white blood cells and platelets, the rotor is rotated at asecond sedimentation speed (about 3200 RPM, usually referred to as “hardspin”).

The rotor is rotated at the selected sedimentation speed for apredetermined period of time that is selected so that, whatever thehematocrit of the blood in the separation bags 1, the blood sediments atthe desired level in each of the separation bag 1 at the end of theselected period. Since, as mentioned above, the density of the hydraulicliquid is selected so as to be between the density of the packed redcells and the density of the plasma, the separation bag 1 will take ahour-glass shape at the end of the sedimentation stage, as shown in FIG.17.

Fourth Stage (Third Protocol): a Plasma Component is Transferred intothe Satellite Bags 2.

At the onset of this stage, the four pinch valve members 70 controllingthe access to the plasma component bags 2 are opened. This causes adecrease in pressure within the separation cells 100 and hydraulicliquid starts flowing again into the hydraulic chambers 103. The raisingvolume of hydraulic fluid in the hydraulic chamber 103 squeezes theseparation bags 1 and causes the transfer of the plasma component intothe first satellite bags 2. Because the hydraulic liquid has a lowerdensity than the density of the packed red blood cells, the red bloodcells remain at the bottom of the separation cell 100 and the separationbags 1 progressively collapse above the red cells as shown in FIG. 18.

When each tube sensor 74 detects blood cells, then the associated pinchvalve member 70 is closed. When the volumes of blood in the fourseparation bags 1 are different, and/or the hematocrit of the blood inthe four separation bags 1 is different (which will be generally thecase), then the four pinch valve members 70 close one after the other.

The fourth stage end when the four pinch valve members 70 are closed.

Fifth Stage (Third Protocol): the Centrifugation Process is Ended.

When the last pinch valve member 70 closes, the rotation speed of therotor is decreased until the rotor stops. The hydraulic liquidsimultaneously drains from the hydraulic chambers 103 into the reservoir120. The red blood cells and the white blood cells remain in theseparation bag 1 (as well as the platelets when the plasma componentcollected is a “platelet poor plasma”).

When the fifth stage is completed, the four bag sets are removed fromthe separation apparatus and each bag set is separately handledmanually.

The breakable stopper 10 blocking the communication between theseparation bag 1 and the tube 6 connected thereto is broken, as well asthe breakable stopper 14 blocking the communication between the secondsatellite bag 3 and the tube 6. The storage solution contained in thesecond satellite bag 3 is allowed to flow by gravity through the filter13 and into the separation bag 1, where it is mixed with the blood cellsso as to lower the viscosity thereof. The content of the separation bag1 is then allowed to flow by gravity through the filter 13 and into thesecond satellite bag 3. The white blood cells and the platelets aretrapped by the filter 13, so that substantially only red blood cells arecollected into the second satellite bag 3.

FIG. 19 shows a fourth embodiment of a separation apparatus for fourdiscrete volumes of a composite liquid.

The main differences between the third separation apparatus shown inFIGS. 13 to 18 and the fourth separation apparatus shown in FIG. 19 areas follows. The fourth separation apparatus does not comprise a fixedreservoir directly connected to the separation chambers, via a conduit,a rotary seal and a rotor duct. The fourth separation apparatuscomprises a hydraulic liquid reservoir 130 that is mounted on the rotor.

The rotor of the apparatus of FIG. 19 comprises a central container 34for satellite bags, having the shape of a cylindrical bucket; aturntable 35 having a frusto-conical wall supporting four separationcells 100 at an angle with respect to the rotation axis 31; theturntable 35 is connected by its smaller diameter section to an upperrim of the central container 34 so as to flare underneath the rim of thecentral container 34; a reservoir 130 for hydraulic liquid, whichcomprises a circular bottom wall 131 and frusto-conical wall 132connected by its smaller diameter section to the circular bottom wall131 and by its larger diameter section to the lower rim of the turntable35 (i.e. the section of the turntable having the larger diameter). Inother words, the interior of the reservoir 130 has a complex geometricalvolume that is symmetrical with respect to the rotation axis 31 and thatis defined by the outside surface or the central container 34, the innersurface of the turntable 35, the inner surface of the frusto-conicalwall 132 of the reservoir, and the inner surface of the bottom wall 131of the reservoir. A rotor shaft 32 is connected to the bottom wall ofthe reservoir 130.

The reservoir 130 is fluidly connected to the hydraulic chamber 103 ofeach separation cell 100 by an outlet aperture 133 through the turntable35 that coincides with the inlet aperture 104 of the hydraulic chambers103. As shown, the outlet apertures 133 are located the farthest fromthe rotation axis 31. With this arrangement, the hydraulic liquid flowsfrom the reservoir 130 into the hydraulic chambers 103 of the separationcells 100 under centrifugal forces as soon as the rotor starts rotating.When the separation apparatus is to be used for separating red bloodcells from plasma (with or without suspended platelets), the density ofthe hydraulic fluid is selected so as to be between the density of packred cells and the density of plasma.

In this fourth embodiment of a separation apparatus, the componenttransferring means essentially comprise the reservoir 130, the hydraulicchambers 103 and the motor 36 that drives the rotor in rotation. Whenthe rotor rotates, the hydraulic liquid drains from the reservoir 130into the hydraulic chambers 103 under centrifugal forces and presses theseparation bags 1 within the separation cell 100 through the elasticdiaphragm 110. The transfer of a separated component from a separationbag 1 into a satellite bag 2 is controlled by the opening/closing of thepinch valve member 70 in which the tube 4 connecting the two bags isinserted.

The first balancing means essentially comprise the reservoir 130, thehydraulic chambers 103 and the motor 36 that drives the rotor inrotation. As soon as the rotor starts rotating, hydraulic fluid flowsfrom the reservoir 130 into the hydraulic chambers 103 until itcompletely fills up the space let vacant in the separation cells 100 bythe separation bags 1, which happens before the rotor has reach thedesired sedimentation speed. The filling up of the space available inthe separation cells 100 with hydraulic liquid might not however resultin an optimal balance of the rotor depending, in particular, on thedifference in weight of the separation bags 1, on their volume, and onthe density of the hydraulic liquid.

It will be apparent to those skilled in the art that variousmodifications can be made to the apparatus and method described herein.Thus, it should be understood that the invention is not limited to thesubject matter discussed in the specification. Rather, the presentinvention is intended to cover modifications and variations.

1. A centrifuge comprising a rotor; more than one container on therotor; a composite fluid chamber in each container on the rotor adaptedto receive a composite fluid; a balancing assembly comprising a sourceof hydraulic liquid; a rotor duct in the rotor directly connected to thesource of hydraulic liquid; an hydraulic chamber in each container onthe rotor wherein the hydraulic chambers are interconnected and areconnected to the rotor duct; and a motor for rotating the rotor whereinrotation of the rotor causes hydraulic liquid to be transferred from thesource to the interconnected hydraulic chambers to balance any unbalancein the rotor due to differences in the composite fluid.
 2. Thecentrifuge of claim 1 further comprising an openable valve between thesource of hydraulic liquid and the rotor duct to control the transfer ofthe hydraulic liquid.
 3. The centrifuge of claim 1 further comprising arotary seal on the rotor to permit distribution of the hydraulic liquidduring rotation of the rotor.
 4. The centrifuge of claim 1 wherein thesource of hydraulic liquid is a reservoir mounted on the rotor.
 5. Thecentrifuge assembly of claim 4 wherein the reservoir defines an internalvolume that is symmetrical with respect to the rotation axis of therotor.
 6. The centrifuge of claim 1 further comprising an elastic socketin each container on the rotor wherein the hydraulic chamber is on oneside of the elastic socket.
 7. The centrifuge of claim 6 wherein theelastic socket is secured to the container to extend between at leasttwo walls of the container.
 8. A method of separating discrete volumesof a composite fluid comprising providing a centrifuge having a rotorand more than one container on the rotor wherein each container containsa hydraulic chamber and a composite fluid chamber adapted to receive acomposite fluid; interconnecting the hydraulic chambers; rotating therotor and the containers on the rotor; separating the discrete volumesof the composite fluid during the rotating step; transferring a volumeof hydraulic liquid into the interconnected hydraulic chambers tobalance the centrifuge comprising connecting a source of hydraulicliquid to the interconnected hydraulic chambers, and distributing by therotation of the rotor the hydraulic liquid from the source to theinterconnected hydraulic chambers.
 9. The method of claim 8 wherein thetransferring step further comprises opening a valve between the sourceof hydraulic liquid and the interconnected hydraulic chambers.
 10. Themethod of claim 8 wherein the distributing step comprises distributinghydraulic liquid from the source through a duct in the rotor to theinterconnected hydraulic chambers.
 11. The method of claim 8 wherein thesource of hydraulic liquid is a reservoir mounted on the rotor and thedistributing step comprises distributing the hydraulic liquid from thereservoir to the interconnected hydraulic chambers.
 12. The method ofclaim 8 wherein the distributing step comprises distributing thehydraulic liquid from the source through a rotary seal to theinterconnected hydraulic chambers.